Due to social energy shortage at present, the whole society is promoting energy saving and environmental protection. In the aspect of lighting, in order to reduce energy consumption, China has enacted “Notice on the Progressive Ban and Sale of Ordinary Lighting Incandescent Lamp” in the year 2011, which provides that the import and sale of ordinary lighting incandescent lamp of 100 watts and above is prohibited nationwide. Therefore, energy-saving lighting lamp will gradually replace ordinary incandescent lamp in the future.
Due to the very high energy conversion rate, low power consumption, long service life, absence of heavy metals and other characteristics, use of LED lamps as energy-saving light source has become a development trend, and LED lamps have gradually replaced the original ordinary energy-saving lamps. Nevertheless, LED lamps have too high light intensity per unit area, and thus dizziness, visual discomfort and other symptoms will occur after direct view. Meanwhile, when LED and LCD are used as display materials, similar problems have also been encountered.
Therefore, when such lamps with bright light are used as a light source or backlight, addition of a material outside is required. When light passes through this material, due to the diffusing effect of the material, point light source can be converted into surface light source, so that the light is softened. This material is called as light diffusing material.
Light diffusing material is mainly used in illumination, including lamps and luminous signs, especially translucent signs of backlight, car skylight, automobile lampshade and so on. In addition, it also has great application value in the aspect of building materials. Roof or greenhouse made of translucent polycarbonate resin can prevent adverse effects caused by direct light, and the plastics far exceeds light diffusing glass in processing performance, and is easily processed and transported. This material can also be used in the display or projection device as scratch-resistant rear projection screen or thin-layer decorative plate.
Polycarbonate resin is a very widely used engineering plastic, and exhibits high light transmittance, but low haze. Some polymethyl methacrylate microspheres, acrylate microspheres or glass beads and other aids are commonly used to increase the haze of the material. However, since the two materials differ in refractive index, light is involved in refraction and absorption on the surface of these particles multiple times. Although the haze of the material is greatly increased, and damage to human eye caused by strong light is reduced, transmittance of light diffusing material is also significantly reduced at the same time, and ultimately only a small part of the energy is converted into light energy, resulting in huge energy consumption.
Chinese patent application CN 101880450 A discloses a process for preparing polycarbonate resin having both high haze and high light transmittance, which process requires addition of polymethyl methacrylate microbeads to polycarbonate to increase haze of the material, wherein a light transmittance of 80% but simultaneously a haze of less than 30% is achieved.
Chinese patent application CN 102250462 A discloses a process for the preparation of light diffusing material using polycarbonate to thereby prepare LED lampshade, in which silicon resin and other light diffusing agent are added to polycarbonate, so that the haze of the material reaches above 90%, but light transmission is only 40%. It cannot be directly used as a light diffusing material.
Therefore, how to prepare a material having improved haze and light transmittance becomes an urgent problem.